Cette thèse porte sur l’étude de la production de surface des ions négatifs (IN) pour des applications dans la fusion thermonucléaire. Ce travail a été réalisé à l'aide d'une source plasma PHISIS. Les IN formés en surface de l'échantillon sont collectés et analysés avec un spectromètre de masse (SM). La fonction de la distribution en énergie des ions négatifs FDEIN est mesurée. Dans cette thèse, une technique de polarisation DC pulsée est introduite pour permettre l'étude de la production d'IN en surface sur des échantillons isolants comme le diamant. Un modèle qui calcule le taux de changement de la variation de la tension sur une surface isolante polarisée en mode pulsé est développé. De façon surprenante, la production d’IN en surface sur un diamant dopé au bore ou non dopé est beaucoup plus élevée en mode pulsé qu'en mode continu. Il est traité également la production d’IN en surface dans les conditions de faible tension de polarisation. Le meilleur rendement d’IN mesuré à faible polarisation est obtenu avec du diamant dopé au bore (BDD) et il est 2 fois plus élevé que celui mesuré sur HOPG (high oriented pyrolitic graphite). L'analyse de la production d’IN en surface à différents polarisations pour différents matériaux a été effectuée afin de corréler l'évolution du rendement d’IN aux changements d'état de surface. Une étude approfondie de la production en surface d'IN a été réalisée sur la surface de Nanoporous 12 CaO. 7Al2O3 electride surface. L'influence des conditions expérimentalles sur le rendement en IN a été étudiée. Dans cette contribution, nous montrons que ce matériau pourrait potentiellement être utilisé dans les sources d'ions négatifs sans césium / This thesis deals with negative ions (NI) surface production for applications in thermonuclear fusion. This work was conducted using a plasma source PHISIS. NI formed on a negatively biased sample surfaceare collected and analyzed with energy mass spectrometer (MS). Negative ion distribution function NIEDF is measured. A SIMION calculation was done to have a complete idea about MS transmission effect on the NIEDF. In the course of this thesis, a DC pulsed bias technique is introduced to enable the study of negative ion surface production on insulating samples as non-doped diamond layers. A model that calculate the rate of change of bias on insulator surface biased in pulsed mode is developed. Surprisingly, negative-ion surface production on boron-doped or non-doped diamond is much higher in pulsed mode than in continuous mode. This thesis deals also with negative ion surface production in low bias condition. The best NI yield measured at low bias is obtained with Boron doped diamond (BDD) ant it is 2 times higher than the one measured on HOPG (highly oriented pyrolytic graphite) surface. Analysis of NI surface production at different surface bias for different material were performed in order to correlate the NI yield evolution to the surface state changes.An extensive study of NI surface production was performed on Nanoporous 12CaO.7Al2O3 electride surface. The influence of surface temperature, bias and plasma exposure time on negative-ion yield was investigated. In this contribution, we show that the electride material has potentials to be used as a production surface in negative ion sources devoted to nuclear fusion application

Heavy-duty trucks are important links in the logistic chains of transport. Critical components in trucks include fuel injectors in which inaccuracies can lead to severe financial damage and higher emissions. Intelligent and efficient ways to detect such scenarios are thus of high importance. This thesis applies machine learning algorithms to measured or estimated engine data, focused on gas exchange signals, to detect inaccuracies in fueling quantities. The fueling inaccuracies considered were of low deviations from the nominal curve, with magnitudes not covered by the currently used fueling diagnostics. The data used for the models was generated from Scania test cell engines where different setups of injectors were deliberately set to over- or underfuel.  Seven different machine learning models were used on the data and evaluated on how well they could detect deviations from nominal fueling. The tests were mainly done with a pure data-driven approach but also improved through different data selection techniques and using domain knowledge. An investigation to connect the findings within the thesis to real customer data was initiated in order to make the results useful for e.g. predictive maintenance. The complications connected to why this was not ultimately achieved were discussed.

Current lean-premixed fuel injector designs have shown great potential in terms of reducing emissions of pollutants, but such designs are susceptible to combustion instabilities in which aerodynamic instability plays a major role and also has an effect on mixing of air and fuel. In comparison to prototype testing with combustors running in operating conditions, computational approaches such as Large Eddy Simulations (LES) offer a much more cost-effective alternative in the design stage. However, computational models employed by LES require validation by experimental data. This is one of the main motivations behind the present experimental study. Combined particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) instrumentation allowed simultaneous measurements of velocity vector and a conserved scalar introduced into the fuel stream. The results show that the inner swirl shear layer features two pairs of vortices, which draw high concentration fuel mixture from the central jet into the swirl stream and causes it to rotate in their wakes. Such periodic entrainment also occurs with the characteristic frequencies of the vortices. This has clear implications for temporal variations in fuel/air ratio in a combusting flow; these bursts of mixing, and hence heat release, could be a possible cause of mixing-induced pressure oscillation in combusting tests. For the first time in such a flow, all 3 components of the turbulent scalar flux were available for validation of LES-based predictions. A careful assessment of experimental errors, particularly the error associated with spatial filtering, was carried out. Comparison of LES predictions with experimental data showed very good agreement for both 1st and 2nd moment statistics, as well as spectra and scalar pdfs. It is particularly noteworthy that comparison between LES computed and measured scalar fluxes was very good; this represents successful validation of the simple (constant Schmidt number) SGS model used for this complex and practically important fuel injector flow. In addition to providing benchmark data for the validation of LES predictions, a new experimental technique has been developed that is capable of providing spatially resolved residence time data. Residence times of combustors have commonly been used to help understand NOx emissions and can also contribute to combustion instabilities. Both the time mean velocity and turbulence fields are important to the residence time, but determining the residence time via analysis of a measured velocity field is difficult due to the inherent unsteadiness and the three dimensional nature of a high-Re swirling flow. A more direct approach to measure residence time is reported here that examines the dynamic response of fuel concentration to a sudden cutoff in the fuel injection. Residence time measurement was mainly taken using a time-resolved PLIF technique, but a second camera for PIV was added to check that the step change does not alter the velocity field and the spectral content of the coherent structures. Characteristic timescales evaluated from the measurements are referred to as convection and half-life times: The former describes the time delay from a fuel injector exit reference point to a downstream point of interest, and the latter describes the rate of decay once the effect of the reduced scalar concentration at the injection source has been transported to the point of interest. Residence time is often defined as the time taken for a conserved scalar to reduce to half its initial value after injection is stopped: this is equivalent to the sum of the convection time and the half-life values. The technique was applied to a high-swirl fuel injector typical of that found in combustor applications. Two test cases have been studied: with central jet (with-jet) and without central jet (no-jet). It was found that the relatively unstable central recirculation zone of the no-jet case resulted in increased transport of fuel into the central region that is dominated by a precessing vortex core, where long half-life times are also found. Based on this, it was inferred that the no-jet case may be more prone to NOx production. The technique is described here for a single-phase isothermal flow field, but with consideration, it could be extended to studying reacting flows to provide more insight into important mixing phenomena and relevant timescales.

L'objectif de cette thèse était trouver des solutions pour produire de hauts rendements d’ions négatifs (IN) H–/D– sur des surfaces dans des plasmas de H2/D2 sans Cs pour des applications en fusion thermonucléaire. La modélisation des fonctions de distribution en énergie des ions négatifs (FDEIN) a montré un accord remarquable avec l'expérience pour les matériaux carbonés. Une méthode de reconstruction mis au point dans le cadre de cette thèse a permis de déterminer les distributions en énergie et en angle des IN émis de la surface. La méthode de reconstruction peut être appliquée à tout type de surface et/ou d’IN. Une étude de la production des IN en surface a été réalisée sur une grande variété de matériaux (des différents types de graphite, couches de diamant et métaux). L'influence sur le rendement des IN de la température de surface, de la tension de polarisation et du temps d'exposition au plasma a été étudiée. Une méthode de polarisation pulsée a été développée pour permettre l'étude de production des IN sur les surfaces de matériaux isolants tels que le diamant microcristallin non dopé. L'utilisation de diagnostics de surface ex situ tels que la désorption programmée en température (DPT) et la spectroscopie Raman ont permis de caractériser l'état de surface des matériaux carbonés. L’ensemble des études a permis de montrer que pour optimiser le rendement des IN sur le diamant, il faut travailler avec une surface moins dégradée. Celle ci peut être obtenu en augmentant la température de surface jusqu’à 400°C – 500°C ce qui permet de restaurer les propriétés intrinsèques des diamants ou en appliquant une polarisation pulsée. / The objective of this thesis was to find solutions to produce high yields of H–/D– negative ions (NI) on surfaces in Cs-free H2/D2 plasmas for thermonuclear fusion applications. Modeling of the negative-ion energy distribution functions (NIEDF) has shown remarkable agreement with experiment for carbon materials. The reconstruction method developed in the course of this thesis has allowed to determine the distribution in energy and angle of NI emitted from the surface. The reconstruction method can be applied to any type of surface and/or NI. A study was performed on a large variety of materials: different types of graphite, diamond films and metals. The influence of surface temperature, bias and plasma exposure time on NI yield was investigated. The method of pulsed bias was developed to enable the study of NI production on surfaces of insulating materials such as microcrystalline non-doped diamond (MCD). The use of ex situ surface diagnostics such as temperature programmed desorption (TPD) and Raman spectroscopy has allowed to characterize the surface state of carbon materials. Basing on the performed studies, we demonstrated that to optimize the NI yield on diamond one has to work with a less degraded surface. This can be obtained rising the surface temperature to 400°C–500°C which allows restoring intrinsic properties of diamond. The less degraded surface state can also be obtained by applying the pulsed bias which gives the possibility to increase the H2/D2 surface coverage and diminish the defects induced by plasma exposure.

Dans le cadre du projet LIU, vise à augmenter la puissance des injecteurs du LHC, le CERN PS Booster (PSB) sera mis à jour avec un système d'injection d'échange de charge H- et son énergie d'injection sera portée de 50 MeV à 160 MeV pour obtenir la luminosité du faisceau nécessaire pour le LHC High-Luminosity Upgrade. Effets de charge d'espace comme pertes de faisceau et incrément d’émittance transversale à l'injection vont être les principales limites vers la réalisation de la haute luminosité souhaitée. Des études sur la dynamique du faisceau en présence de charge d'espace afin d'évaluer les performances du PSB après la mise à niveau ont été effectuées. La première partie du travail consiste de mesures dans la présente machine, pour étudier les effets de charge d'espace et son interaction avec les résonances et d'avoir un ensemble de données pour le code benchmarking. Le code choisi pour le suivi du faisceau en présence de charge d'espace est PTC-Orbit (et PyOrbit). Les études de convergence numériques nécessaires sont présentées conjointement avec les études de la comparaison des simulations avec les mesures dans la machine. Une fois évalué le code et ses limites, les prévisions pour l'injection dans le PSB à 160 MeV avec des poutres de luminosité élevé sont livrés en termes de pertes de faisceau et incrément d’émittance. Ces études comprennent l'optimisation du point de fonctionnement, la compensation des résonances et/ou la correction de chromaticité en tenant compte des erreurs magnétiques attendus dans la machine. / As part of the LHC Injector Upgrade Project, the CERN PS Booster (PSB) will be upgraded with a H- charge exchange injection system and its injection energy will be raised from 50 MeV to 160 MeV to obtain the beam brightness required for the LHC High-Luminosity Upgrade. Space charge effects like beam losses and transverse emittance blow-up at injection are expected to be the main limitations towards the achievement of the required high brightness. Studies of beam dynamics in presence of space charge in order to evaluate the performances of the PSB after the Upgrade have been performed. The first part of the work consists of measurements in the present machine, to study the effects of space charge and its interplay with resonances and to have a good set of data for code benchmarking. The code chosen for the beam tracking in presence of space charge is PTC-Orbit (and PyOrbit). Necessary numerical convergence studies are presented together with a benchmark with the PSB measurements. Once assessed the code and its limitations, predictions for the 160 MeV injection with high- brightness beams are delivered in terms of beam losses and emittance blow-up. These studies include the optimization of the working-point, resonance compensation and/or chromaticity correction taking into account the expected magnetic errors in the machine.

The main target of this thesis is to choose the suitable hard filled wax for the invest-ment casting foundry Fimes a.s. There are several suppliers of these waxes in the World and in this work waxes of the most reputable suppliers from Europe have been investigated. During these tests there were mainly technological properties of the waxes and also dimensions of both wax patterns and also the final castings measu-red. Suitability of the tested waxes, their technological characteristics, analysis of di-mensions and finally basic economical calculations have been then used in this the-sis as a tool for the recommendation for the most suitable wax for the Fimes foundry.

The purpose of the study was to explore the experiences of female nyaope injectors residing in City of Tshwane Municipality, Gauteng. The study was conducted at COSUP sites namely; Soshanguve, Pretoria CBD, Sunnyside, Mamelodi, Eersterust, and Attridgeville. The study focused on females who have a history of injecting nyaope, accessing substance use related services at a registered service provider within City of Tshwane Municipality, Gauteng. Research design of the study was exploratory, which is basically used to explore a new topic or learn more about phenomenon where little is known. The research approach was purely qualitative methodology. This permitted the researcher to deeply explore the lived experiences of female nyaope injectors residing in City of Tshwane Municipality, Gauteng. A qualitative in-depth interview method was used to collect data from 24 participants who took part in the study. Questions of the interview were semi-structured, in-depth one-on-one interviews and were used to explore the lived experiences of female nyaope injectors residing in City of Tshwane Municipality, Gauteng. The findings of the study revealed that females who are injecting nyaope, are at risk of contracting HIV and other blood-borne infections. The stigma that is perpetuated by families, intimate partners, communities, health care professionals, and police officers is creating a hostile environment for female nyaope injectors; which increases the risk of contracting HIV and other blood-borne infections. Harm reduction services have the potential to address the needs of female nyaope injectors if fully implemented. It can be concluded that there is a need for substance abuse service providers to implement comprehensive harm reduction services to curb HIV prevalence amongst female nyaope injectors. / Health Studies / M.A. (Social Behavioural Studies in HIV/AIDS)